Method for the liquid disintegration of metal



Feb. 18, 1969 Filed June 22,

E. E. V. HELIN ETAL METHOD FOR THE LIQUID DISINTEGRATION OF METAL Sheet(111 I! 1 1 111,, 11:11 11 11' lllllllflllll' fig. 6a

METHOD FOR THE LIQUID D ISINTEGRATIQN OF METAL Filed June 22. 1965 Feb.18, 1969 E. E. v. HELIN ETAL Sheet y/vm/s zH/MITMQWMZM BY U UnitedStates Patent 8,363/ 64 US. Cl. 264-11 9 Claims Int. Cl. B22d 23/08ABSTRACT OF THE DISCLOSURE The method of disintegrating metal comprisingthe steps of projecting a stream of molten metal, projecting a stream ofcondensible vapor to a zone adjoining said stream of molten metal, andcausing the stream of vapor to condense rapidly in said zone, whereby avigorous agitation is produced in said zone to disintegrate said streamof metal into a shower of discrete particles.

The invention relates to the production of metal powder or metalgranules directly from molten metal by the action of a jet or blast of afluid subdividing agent on a stream or jet of the molten metal, withoutthe aid of rotary vanes or other mechanical means for shattering thestream of molten metal. The term metal is used throughout thisspecification to denote pure metals as well as alloys, for instanceferroalloys, alloy steels, non-ferrous alloys and the like metals.

The invention has for its principal object to provide a method for theproduction of a powder or a granulated product consisting ofcomparatively coarse particles, for instance with particle sizesexceeding /2 mm. and having a rounded or at least compact particle shape(in contradistinction to jagged or extended particles). Powders orgranules (shot) of this type have many uses, for instance as blastingagents in the shot blasting process, or as materials for some powdermetallurgical processes, for instance direct rolling of metal strip frompowder.

Another object is the provision of a liquid disintegration method ofproducing coarse metal powders which yields a high proportion ofparticles of uniform size.

Still another object is the provision of a liquid disintegration methodof making metal powder which is suitable for the production of coarsepowders consisting of stainless steel and other steels containingchromium.

According to an important feature of the invention, the stream or jet ormetal to be disintegrated is submitted to the action of steam (or anyother suitable condensible vapour) which is in a state of rapidcondensation induced by the action on the steam of a fluid coolant, suchas air or nitrogen or water. The rapid condensation of the steamgenerates implosions and resulting in a very vigorous mechanicalagitation of the molten metal promoting the shattering of the stream ofmolten metal into discrete particles. Preferably the steam and/or thecoolant are supplied to the disintegration zone as jets projected on tothe stream of molten metal at such a velocity as to contributesubstantially to the breaking up of the metal stream and the removal ofthe particles formed.

Other objects and. features of the invention will be clear from thefollowing description taken in connection with the accompanyingdrawings, in which:

FIG. 1 represents a form of apparatus by which the invention may becarried out, in vertical section;

FIG. 2 depicts another form of such apparatus in vertical section, theupper part only of the apparatus being shown;

3,428,718 Patented Feb. 18, 1969 FIG. 3 is a view taken below thedischarge nozzles towards the underside of the tank lid in FIG. 2;

FIGS. 4 and 5 depict as in FIGS. 2 and 3, respectively, a third form ofthe apparatus for carrying out the invention;

FIG. 6 represents still another form of the apparatus by means of whichthe invention may be practised, in fragmentary vertical section; and

FIG. 6a is a view from below of the pouring pot which forms part of theapparatus according to FIG. 6.

Stating it broadly, the method aspects of the invention comprisesprojecting a stream of metal to a zone, projecting a stream ofcondensible vapourto the zone so as to contact said stream of metal insubstantially the zone, and causing the stream of vapour to condenserapidly in said zone, whereby to set up a vigorous agitation in the zoneto disintegrate the stream of metal into a shower of discrete particles.The particles are then allowed to cool while falling from the zone ofdisintegration and then collected in a quenching fluid, such as a poolof water.

In its broad aspects, the apparatus employed for carrying out theinvention comprises means for discharging a stream of molten metal to azone, means for directing at least one jet of condesible vapour towardsthe stream of molten metal in said zone, and means for supplying acooling agent to the at least one jet of vapour so as to produce a rapidcondensation of the vapour resulting in a vigorous agitating action inthe zone where the vapour jet contacts the stream of metal. Preferablyit has been found advantageous to discharge the metal through aslit-shaped orifice whereby to present the metal stream with aribbon-like shape.

In the apparatus according to FIG. 1, a pouring trough inclined about 30towards the horizontal plane is adapted to receive molten metal from aladle 2 and to discharge or project it as a ribbon-shaped stream or jet3 into the interior of a disintegration tank 4. A nozzle 7 connected toa steam conduit 5 through a reduction valve 6 is disposed a little belowthe trough 1 and discharges a jet of steam towards the molten metal jet.The axis of the nozzle is substantially parallel to the trough 1,resulting in an acute angle of contact with or impact of the steam jeton the jet of molten metal. The degree of saturation of the emergingsteam, the velocity of the steam jet and the distance -between thenozzle and the region in which the jets of steam and metal meet are soadjusted that rapid condensation occurs induced by the surroundingcolder air. This is accompanied by vigorous agitation caused byimplosions in the region in which the jets of steam and metal meet. Thepresence of the conditions referred to above can be ascertained in asimple manner by means of a feeler, for instance a wooden stick,inserted into the steam jet. The onset of the desired conditions ismarked by strong irregular vibrations in the feeler. It is importantthat the feeler be held in just the portion of the jet which is tostrike the liquid metal. The conditions described result in a veryeffective disintegration of the liquid metal into particles. Theparticles are caught by a water bath 8 in the disintegration tank. Thedistance between the disintegration zone and the surface of the waterbath should preferably be sufficient to allow the falling particles toassume a rounded shape and to solidify prior to hitting the surface ofthe bath.

The conditions prevailing in the disintegration zone describedhereinbefore are important for disintegrating the molten metal intorounded particles of fairly equal size. If the conditions are allowed tochange so that the rapid condensation process is not fully developed(that is, if the length of the steam jet is reduced or if the velocityand/ or the superheating of the steam are increased), inferior resultswill be obtained. The result will, of course, also be impaired if therapid condensation process occurs substantially in front of the zone inwhich the steam jet meets the metal jet. This is because the energy ofthe condensation process expends itself prematurely. Preferablesaturated (or only slightly superheated) steam is supplied to the nozzleat comparatively low pressure, approximately 7 to 15 p.s.i.g. Ifdesired, the superheating of the steam can be controlled by the knownmethod of injecting water into the steam conduit. For convenience, thezone in which the foregoing conditions are met is referred to as thezone of disintegration.

In the apparatus according to FIG. 1 the desired con- .densation in thesteam jet is induced by the admixture of surrounding colder air admittedthrough the opening in the roof of the disintegration tank, theadmixture being effected by the action of the turbulence of the steamjet. A more effective control of the intensity and the localization ofthe desired condensation phenomena can be obtained by supplying at leastpart of the colder fluid t the steam jet in the form of jets out of oneor several nozzles. This methol is employed in the embodiments accordingto FIGS. 2-6.

In the embodiment according to FIGS. 2 and 3, the liquid metal isdischarged as a flattened or ribbon-shaped jet 11 through a slit-shapedorifice 9 in the bottom of a pouring pot 10. A pair of nozzles 12, 13are provided in the disintegration tank 14, each of which is adapted todischarge a steam jet towards one side of the metal jet. In thearrangement shown, the steam jets are symmetrically disposed with regardto the plane of the metal jet. It is, however, also possible to have thesteam jets form different angles to the plane of the metal jet and/ orto make one steam jet strike the plane of the metal jet at a spotvertically offset with regard to the spot at which the other steam jethits the plane of the metal jet in substantially the zone ofdisintegration. A twin nozzle 15 supplied with a compressed coolingagent, for instance water or nitrogen, is provided with a plurality ofdischarge orifices 16 for the formation of jets 17 of the cooling agentdirected so as to form a pair of curtains of cooling jets whichencounter the steam jets slightly in front of the spots in which thesteam jets strike the metal jet. In the zone in which steam and coolingagent are mixed there occurs an intense condensing action attended byimplosions providing an effective disintegration of the molten metalinto coarse particles. The disintegrating process is assisted by thedynamic action of the jets of cooling agent and steam upon the liquidmetal. In the embodiment shown, the orifices 16 are directed so as tomake the jets 17' form an angle of about 20 with the metal jet 11. Theangle in question is not critical, but should generally not exceed 30.The angle of convergence between the cooling jets 17' and the steam jetsshould be sufficiently large in order to provide a sudden and thoroughcondensation of the steam within a limited condensation zone. Generally,said angle of convergence should not be below 10.

,so that the angle of convergence between the steam jet and the jet ofcooling agent amounts to about 60. The choice of an angle of convergenceexceeding 90 is apt to result in unfavourable conditions in thedisintegration zone and should be avoided.

In order to minimize oxidization of the metal in the liquiddisintegration apparatus shown in FIGS. 2 to in the case in which thecooling agent consists of water or some other liquid, a nonoxidizing gassuch as nitrogen may be supplied to the disintegration chamber from aseparate source. In most cases, however, this step may be dispensedwith. The apparatus shown in 'FIG. 1, in which the atmospheric air formsthe cooling agent, has,

indeed, been used successfully for the disintegration of susteniticstainless steel of the type containing about 18% chromium and 8% nickel.

In the embodiment according to FIG. 6, the steam nozzles 19 as well asthe cooling agent nozzles 20 are set at acute angles less than 45 to theplane of the metal jet. The metal particles produced by thedisintegration of the metal jet are in this embodiment accelerated to alarge downward velocity by the combined action of the jets of steam andcooling agent. The disintegration tank therefore must have acomparatively large height in order to give the particles sufficienttime to assume a rounded shape (and to solidify, if this is required).In order to ensure an effective mixing of the steam and the coolingagent (for instance nitrogen) in the condensation zone in thearrangement according to FIG. 6, the condition should be chosen so as tomake the discharge velocity of the cooling agent substantially differentfrom the one of the steam. The pouring pot 21 is provided with a row ofround bottom holes 22 instead of one single slitshaped orifice. Thisarrangement is sometimes preferable in such cases in which the metal jetdischarged from a slit-shaped orifice has a tendency to contractlaterally as a result of a high surface tension and/or a large verticaldistance between the orifice and the disintegration zone.

As illustrative of the advantages of the invention, the followingexamples are given:

EXAMPLE I In a liquid disintegration plant of the type shown in FIG. 1used for the production of stainless steel powder, the discharge orificeof the nozzle 7 forms a horizontally extending slot having a length ofmm. (4 in.) and a width of 2.8 mm. (0.11 in.). The groove of the trough1 has a width of 65 mm. (2.56 in.). The vertical distance from thedischarge orifice of the nozzle to the surface of the pool of water 8amounts to about 650 mm. (26 in.). The water is preheated to atemperature not below 60 C. F). Saturated steam at a pressure of about 1kg./cm. (l4 p.s.i.g.) is supplied through the conduit 5 and dischargedthrough the nozzle 7 for a period of about half a minute before startingthe disintegration process; during this period, the flow of steamemerging from the nozzle 7 is adjusted by means of the valve 6 in such amanner as to make the zone of rapid condensation in the steam jetcoincide with the zone in which the steam jet will meet the jet ofmolten metal (the disintegration zone), a simple way to achieve thiscondition being to insert an elongated wooden feeler into the intendedzone of disintegration and adjust the steam flow until strong irregularvibrations are sensed through the Wooden feeler. A molten charge ofstainless steel composed of:

Percent (about) Chromium 18 Nickel 8 Silicon 0.6 Manganese 1 Balancesubstantially iron.

EXAMPLE II In a plant of the type shown in FIGS. 2 and 3, the dischargeorifice 9 in the bottom of the pouring pot 10 has a length of 30 mm.(1.18 in.) and a width of 5 mm. (0. 2 in.). The discharge orifice ofeach of the steam nozzles 12, 13 has a length of 40 mm. and a width of 3mm. The twelve (2X6) discharge orifices of the twin nozzle 15 each havea diameter of 3 mm. (0.12 in.), their centre-to-centre spacing being 6mm. (0.24 in.). The nozzles 12, 13 are supplied with saturated steam ata pressure of about 0.8 kg./cm. '(11.5 lbs./sq. in.), While the twinnozzle 15 is supplied with compressed air from a compressed airdistribution network through a reduction valve adjusted to provide aflow of compressed air resulting in the desired condition of suddencondensation at the zone in which the jets 17' of compressed airpenetrate into the jets of steam emitted by the nozzles 12, 13, thepresence of said condition manifesting itself by strong irregularvibrations in a feeler or test stick inserted into the centre of thedesired disintegration zone. The vertical distance from thedisintegration zone to the surface of the water bath in the lower partof the tank 14 is about 9 feet. -A molten steel bath composed of:

is poured into the pouring pot '10 at a temperature of 1600" C. at sucha rate as to maintain a head of liquid metal of about 4 in. in the potwhile a continuous ribbon-like stream of metal flows through theslot-shaped orifice 9 into the zone of disintegration. The metal iscontinuously disintegrated into small particles which are allowed tofall freely and solidify into rounded or spheroidal grains beforefalling into the pool of quenching water. The particle size of theproduct is fairly uniform, with a small proportion only of dines havinga size below 0.5 mm.

The method and apparatus of the invention may be applied to theproduction of a variety of metal powders such as the following: themetal iron and alloys thereof, such as 86% Fe-14% Cr; 82% Fe-l8% Cr; 73%Fe-27% Cr; 74% Fe-l8% Cr-8% Ni; 53% Fe-25% Ni-16% Cr-6% Mo; low, mediumand high alloy tool steels and the like; the metal nickel and alloysthereof, such as 80% Ni-20% Cr; 80% Ni-14% Cr-6% Fe; 73.8% Ni-15% Cr-7%Fe-1% Cb-2.5% Ti-0.7% Al; cobalt and cobalt-base alloys and such othernon-ferrous metals as copper and the commercially known copper-basealloys.

An important advantage of the invention is that because the particlesproduced are substantially uniform in size, they exhibit uniform packingdensities and, moreover, are characterized by free-flowing properties.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention as those skilled in the art will readilyunderstand.

What is claimed is:

1. A method of disintegrating metal comprising:

(a) projecting a stream of condensible vapor into a zone,

(b) causing a cooling fluid to be brought into said zone to contact saidvapor stream to cause rapid condensation of said vapor and a resultingvigorous agitation within said zone,

(c) projecting a molten stream of said metal into said zone and in amanner for said vigorous agitation to be directed upon said metal streamto cause shattering of said metal into discrete particles,

(d) allowing said metal particles to fall into a quenching fluid to cooland solidify, and A (e) removing the metal particles thus produced.

2. The method of claim 1, wherein the condensible vapor is saturatedsteam.

3. The method of claim 1, wherein the condensible vapor is superheatedsteam.

4. The method of claim 1, wherein the cooling fluid is water.

5. The method of claim 1, wherein the cooling fluid is nitrogen.

6. The method of claim 1, wherein the quenching fluid is water.

7. The method of claim 1, wherein the zone is enclosed and vented.

8. The method of claim 1, wherein said cooling fluid is brought intosaid zone as a plurality of thin jets to contact said vapor stream.

9. The method of claim 8, wherein said cooling fluid is projected at anangle not exceeding 30 degrees with the axis of fiow of said moltenstream of metal.

References Cited UNITED STATES PATENTS 2,070,134 2/1939 Keyes 264-122,315,735 4/ 1943 Richardson 264-12 3,104,164 9/ 1963 Osborne 2648FOREIGN PATENTS 587,343 11/1959 Canada.

ROBERT F. WHITE, Primary Examiner.

JAMES R. HALL, Assistant Examiner.

U.S. Cl. X.R. 26412

